Variable valve lift apparatus

ABSTRACT

A variable valve lift apparatus including an inner tappet, an outer tappet surrounding and slidably contacting the inner tappet, and a latching pin slidably inserted into the inner tappet so as to implement a high lift and a low lift by selectively joining the inner tappet and the outer tappet may include a stopper partially inserted into the outer tappet and spaced apart from the latching pin in a movement direction of the latching pin so as to limit movement of the latching pin, and forming a latching pin joining groove in the outer tappet to selectively receive the latching pin, wherein the stopper partially projects to the outside of the outer tappet and is slidably engaged to a cylinder head groove formed to a cylinder head bore to prevent the variable valve lift apparatus from being rotated.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2010-0095559 filed in the Korean Intellectual Property Office on Sep.30, 2010, the entire contents of which is incorporated herein for allpurposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable valve lift apparatus, andmore particularly, to a variable valve lift apparatus with a stopperthat is inserted into an outer tappet to limit movement of a latchingpin and projects to the outside of the outer tappet and slides in acylinder head groove to prevent the variable valve lift apparatus frombeing rotated.

2. Description of Related Art

In general, an internal combustion engine receives fuel and air in acombustion chamber and combusts the fuel and air to form power. Anintake valve is actuated by driving a cam shaft at the time ofsuctioning air and air is suctioned into the combustion chamber whilethe intake valve is opened. Further, an exhaust valve is actuated bydriving the cam shaft and air is discharged from the combustion chamberwhile the exhaust valve is opened.

However, an optimal operation of the intake valve/exhaust valve dependson a rotational velocity of an engine. That is, an appropriate lift orvalve opening/closing time depends on the rotational velocity of theengine. As such, in order to implement the appropriate valve operationdepending on the rotational velocity of the engine, a variable valvelift (VVL) apparatus in which a cam driving the valve is designed tohave a plurality of shapes or the valve is implemented to operate indifferent lifts depending on the number of rotations of the engine hasbeen researched.

FIG. 9 is a cross-sectional view of a variable tappet in a high liftmode of a known variable valve lift apparatus and FIG. 10 is across-sectional view of a variable tappet in a low lift mode of a knownvariable valve lift apparatus.

First, in the high lift mode, oil pressure is supplied to a hydraulicchamber 240 formed in an outer tappet 100 and a plunger 350 pushes alatching pin 310 by the supplied oil pressure. Therefore, as shown inFIG. 9, the latching pin 310 is inserted into a latching pin joininggroove 340 and an inner tappet 200 and the outer tappet 100 are joinedto each other.

In this case, a high cam 12 is joined to a cam shaft 10, such that thehigh cam 12 presses the outer tappet 100 by rotation of the cam shaft10, and as a result, the outer tappet 100 and the inner tappet 200integrally move up and down. That is, high lift is executed byrotational movement of the high cam 12.

On the contrary, in the low lift mode, the oil pressure of the hydraulicchamber 240 formed in the outer tappet 100 is released and the latchingpin 310 moves with being separated from the latching pin joining groove340 by a restoring force of a return spring 330, as shown in FIG. 10.The inner tappet 200 and the outer tappet 100 are separated from eachother by the movement of the latching pin 310 and independently move. Inthis case, a latching pin supporting pin 320 supports the return spring330 and is inserted into the inner tappet 200.

The valve is opened and closed by the inner tappet 200 that reciprocatesby rotation of a low cam 14 joined to the cam shaft 10 and the outertappet 100 merely moves up and down by a lost motion spring 500 (seeFIG. 4) depending on the rotation of the high cam 12 and has noinfluence on the opening and closing of the valve.

However, if the cams 12 and 14 and surfaces of the tappets 100 and 200of the variable valve lift apparatus do not coincide with each other,respectively, the variable tappets 100 and 200 rotate, and as a result,the engine is damaged.

Further, since a working fluid can be supplied only when positions of asupply hole of the working fluid actuating the variable valve liftapparatus and a working fluid supplying hole of a bore of a cylinderhead coincide with each other, an additional rotation preventing devicefor preventing rotation of the entire variable valve lift apparatus isrequired.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing avariable valve lift apparatus with a stopper capable of limitingmovement of a latching pin while allowing cams and tappet surfaces ofthe variable valve lift apparatus to coincide with each other bypreventing the variable valve lift apparatus from being rotated.

A variable valve lift apparatus including an inner tappet, an outertappet surrounding and slidably contacting the inner tappet, and alatching pin slidably inserted into the inner tappet so as to implementa high lift and a low lift by selectively joining the inner tappet andthe outer tappet, may include a stopper partially inserted into theouter tappet and spaced apart from the latching pin in a movementdirection of the latching pin so as to limit movement of the latchingpin, and forming a latching pin joining groove in the outer tappet toselectively receive the latching pin, wherein the stopper partiallyprojects to the outside of the outer tappet and may be slidably engagedto a cylinder head groove formed to a cylinder head bore to prevent thevariable valve lift apparatus from being rotated.

The stopper may include an insertion portion having substantially thesame diameter as the latching pin and being inserted into the outertappet to limit the movement of the latching pin, and a projectionportion projecting from the insertion portion to the outside of theouter tappet and having a shape to be slidably inserted into thecylinder head groove in order to prevent the variable valve liftapparatus from being rotated.

The projection portion may have a semi-spherical shape which may beslidable while contacting the cylinder head groove.

The projection portion may have a semi-cylindrical shape formed in amovement direction of the outer tappet and slides while contacting thecylinder head groove.

A through-hole may be formed in the stopper and fluid-connected to thelatching pin joining groove to smoothly discharge oil pressure suppliedto actuate the latching pin.

The insertion portion may have a cylindrical shape having the sameradius as the latching pin.

According to the exemplary embodiments of the present invention, it ispossible to prevent an engine from being damaged by internally limitinga movement distance of a latching pin and externally preventing avariable valve lift apparatus from being rotated, make supply of aworking fluid smooth, and save a manufacturing cost because anadditional rotation preventing device does not need to be processed in atappet skirt part.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a variable tappetaccording to an exemplary embodiment of the present invention.

FIG. 2 is a plan view of a variable tappet according to an exemplaryembodiment of the present invention.

FIG. 3 is a perspective view of a state in which inner and outer tappetsare partially cut according to an exemplary embodiment of the presentinvention.

FIG. 4 show a use state diagram before and after a variable valve liftapparatus according to an exemplary embodiment of the present inventionis joined to a cylinder head and an enlarged diagram of a principalpart.

FIG. 5 is a perspective view of a variable tappet according to variousexemplary embodiments of the present invention.

FIG. 6A to 6D are a perspective view, a plan view, a side view, and afront view of a stopper according to various exemplary embodiments ofthe present invention.

FIG. 7 is a perspective view of a variable tappet according to variousexemplary embodiments of the present invention.

FIGS. 8A to 8D are a perspective view, a plan view, a side view, and afront view of a variable tappet according to various exemplaryembodiments of the present invention.

FIG. 9 is a cross-sectional view of a variable tappet in a high liftmode of a known variable valve lift apparatus.

FIG. 10 is a cross-sectional view of a variable tappet in a low liftmode of a known variable valve lift apparatus.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown.

FIG. 1 is a longitudinal cross-sectional view of a variable tappet of astate in which a stopper is joined to the variable tappet according toan exemplary embodiment of the present invention and FIG. 2 is a planview of a variable tappet according to an exemplary embodiment of thepresent invention.

FIG. 3 is a perspective view of a state in which inner and outer tappetsare partially cut according to an exemplary embodiment of the presentinvention, FIG. 4 is a use state diagram before and after a variablevalve lift apparatus according to an exemplary embodiment of the presentinvention is joined to a cylinder head, FIG. 5 is a perspective view ofa variable tappet according to a first exemplary embodiment of thepresent invention, and FIG. 6A to 6D are a perspective view, a planview, a side view, and a front view of a stopper according to a firstexemplary embodiment of the present invention.

First, referring to FIGS. 1 to 6A to 6D, a stopper 400 that is providedto be spaced apart from a latching pin 310 at one upper side of an outertappet 100 in a movement direction of the latching pin 310 is providedin the outer tappet 100. In the above description, the latching pin 310may be partially a hollow body and have a cylindrical shape. A latchingpin supporting pin 320 limiting movement of the latching pin 310 whilepenetrating the latching pin 310 is joined to an inner tappet 200. Areturn spring 330 that restores the latching pin 310 to an originalstate when oil pressure is released, while contacting the latching pinsupporting pin 320, is inserted into the latching pin 310.

Referring to FIGS. 4 and 5, the stopper 400 includes an insertionportion 410 having the same shape as the latching pin 310 to limithorizontal movement of the latching pin 310 and a projection portion 420having a similar shape to a plan cross section of a groove 110 to slidewhile projecting to the outside of the outer tappet 100 and contactingan inner circumference of the groove 110 of a cylinder head. Theinsertion portion 410 may be a cylindrical shape having the same radiusas the latching pin 310.

An exemplary embodiment of the present invention will hereinafter bedescribed in more detail with reference to the accompanying drawings.

In the variable valve lift apparatus, an auxiliary latching pin 370pushes the latching pin 310 by oil pressure supplied at the time whenthe oil pressure is supplied through a hydraulic chamber 360 and thelatching pin 310 in the inner tappet 200 moves to one inner side of theouter tappet 100, such that the inner tappet 200 and the outer tappet100 are joined to each other. In this case, a distance in which thelatching pin 310 can move is limited to a movement limiting distance A.

As such, the latching pin 310 selectively joins the outer tappet 100 andthe inner tappet 200 while moving in a horizontal direction in order tocontrol a valve lift, thereby implementing a high lift or a low lift. Inthis case, when the supplied oil pressure is excessively large, thelatching pin 310 may move excessively. In order to prevent the excessivemovement of the latching pin 310, the latching pin 310 should move onlywithin the movement limiting distance A in which the latching pin 310can move. In the exemplary embodiment of the present invention, thestopper 400 serves to such a function. Further, the projection portion420 that projects to the outside of the outer tappet 100 is engaged inthe groove 110, and as a result, the variable valve lift apparatus maymove up and down without rotating. Therefore, since surfaces of theinner and outer tappets 100 and 200 coincide with a high cam 12 and alow cam 12 in a rotational direction, it is possible to prevent anengine from being damaged.

FIG. 4 shows a use state diagram showing a state in which the stopper400 according to the exemplary embodiment of the present invention ispositioned in a cylinder head groove with being partially exposed to theouter tappet 100 and an enlarged diagram of a principal part. A leftside of FIG. 5 shows a state in which a tappet is inserted into a boreof a known cylinder head and a right side of FIG. 5 shows a state inwhich the stopper 400 according to the exemplary embodiment of thepresent invention is inserted into the cylinder head groove 110.Further, the enlarged diagram of the principal part shows a state inwhich the stopper 400 is engaged in the cylinder head groove 110.

The projection portion 420 of the stopper 400 should have a structure toslide on an inner circumference of the cylinder head groove in order toprevent the variable valve lift apparatus from being rotated. That is,when a plan cross section of the inner circumference of the cylinderhead groove 110 has a semi-spherical shape, a plan cross section of theprojection portion 420 should also have the semi-spherical shape.

Therefore, in the first exemplary embodiment of the present invention,as shown in FIG. 6B, the plan cross section of the projection portion420 may have the semi-spherical shape. Further, since the projectionportion 420 should slide on the inner circumference of the cylinder headgroove 110, the projection portion 420 may have a semi-cylindrical shapethat is long in a vertical direction which is a movement direction, asshown in FIGS. 5 and 6. In addition, a through-hole 430 is formed at thecenter of the stopper 400 by passing through the insertion portion 410and the projection portion 420. The formation of the through-hole 430 isto easily discharge the oil pressure after actuating the latching pin310 to the outside.

A second exemplary embodiment is shown in FIGS. 7 and 8A to 8D.According to the second exemplary embodiment, a projection portion 460may have a semi-spherical shape. In this case, an insertion portion 450has a cylindrical shape as shown in FIG. 7, and since the insertionportion 450 has a through-hole 470 formed at the center thereof asdescribed in the first exemplary embodiment, the insertion portion 450has a structure to easily discharge preused oil pressure. When thestopper 400 is manufactured as described in the second exemplaryembodiment, the stopper 400 can be more easily manufactured than thestopper 400 in the first exemplary embodiment.

As described above, it is possible to limit excessive horizontalmovement of the latching pin 310 by the insertion portions 410 and 450having the cylindrical shape, which are inserted into the outer tappet100 and prevent the variable valve lift apparatus from being rotated bythe projection portions 420 and 460 that project to the outside of theouter tappet 100. It is possible to make supply of a working fluidsmooth by allowing positions of a working fluid supplying hole and asupplying hole on a surface of a cylinder head bore 120 to coincide witheach other as the variable valve lift apparatus is prevented from beingrotated. Further, rotation surfaces of the high cam 12 and the low cam14 of the variable valve lift apparatus coincide with the surfaces ofthe outer tappet 100 and the inner tappet 200, respectively, therebypreventing the engine from being damaged.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “inner” and “outer” are used todescribe features of the exemplary embodiments with reference to thepositions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof. It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

1. A variable valve lift apparatus including an inner tappet, an outertappet surrounding and slidably contacting the inner tappet, and alatching pin slidably inserted into the inner tappet so as to implementa high lift and a low lift by selectively joining the inner tappet andthe outer tappet, the apparatus comprising: a stopper partially insertedinto the outer tappet and spaced apart from the latching pin in amovement direction of the latching pin so as to limit movement of thelatching pin, and forming a latching pin joining groove in the outertappet to selectively receive the latching pin, wherein the stopperpartially projects to the outside of the outer tappet and is slidablyengaged to a cylinder head groove formed to a cylinder head bore toprevent the variable valve lift apparatus from being rotated.
 2. Theapparatus of claim 1, wherein the stopper includes: an insertion portionhaving substantially the same diameter as the latching pin and beinginserted into the outer tappet to limit the movement of the latchingpin; and a projection portion projecting from the insertion portion tothe outside of the outer tappet and having a shape to be slidablyinserted into the cylinder head groove in order to prevent the variablevalve lift apparatus from being rotated.
 3. The apparatus of claim 2,wherein the projection portion has a semi-spherical shape which isslidable while contacting the cylinder head groove.
 4. The apparatus ofclaim 2, wherein the projection portion has a semi-cylindrical shapeformed in a movement direction of the outer tappet and slides whilecontacting the cylinder head groove.
 5. The apparatus of claim 2,wherein a through-hole is formed in the stopper and fluid-connected tothe latching pin joining groove to smoothly discharge oil pressuresupplied to actuate the latching pin.
 6. The apparatus of claim 2,wherein the insertion portion has a cylindrical shape having the sameradius as the latching pin.